川渝地区夏季旱涝与海温异常浅析

Analysis of Floods and Droughts in Chongqing and East Sichuan

利用1951—2006年6—8月降水资料计算了川渝地区旱涝指数Z指数,确定出该区域旱涝等级及其对应年份,分析这一带历年旱涝情况及年际变化特征,并用相关和合成分析法分析旱涝与海温的关系。结果表明,1950年代末至1970年代前期,这一带地区以旱为主,3个重旱年有2年出现在这个时段内;1970年代末至2003年,旱涝年均有,但以涝为主,2006年则出现了1951年以来最旱的年份。旱涝指数与SST的相关分析显示Z指数与前期SST,特别是1—3月SST有较好的相关关系,Z指数与赤道中东太平洋SST显著正相关。重涝年赤道中东太平洋广大海域SST呈明显的正距平,而重旱年则为大范围SST负距平。2006年1—3月赤道中东太平洋海温呈明显负距平、南太平洋20°S以南到40°S之间海域海温呈显著正距平有利于川渝地区出现严重干旱。

Summer floods and droughts from 1951 to 2006 in Chongqing and East Sichuan are analyzed here by using Z index. It shows that droughts are popular from the end of 1950s to early 1970s, 2 of the 3 most heavy years occur during this period. There are both droughts and floods from the end of 1970s to 2003 , but floods are more common. 2006 is the most serious drought year in these 56 years from 1951 to 2006. Relation analyses between SST and Z index shows that there exists good relativity between Z index and SST during January and March. Z index has obviously positive relativity with SST in eastern and medial equatorial pacific ocean. In heavy floods year SST anomalies are prominently positive. On contrast in droughts years, SST anomalies are obviously negative. Negative anomalies from January and March are contributable for the serious droughts in 2006.